Gas hydrate dissociation off Svalbard induced by isostatic rebound rather than global warming

Wallmann, Klaus; Riedel, Michael; Hong, Wei‐Li; Patton, Henry; Hubbard, Alun; Pape, Thomas; Hsu, Chieh Wei; Schmidt, Christopher J.; Johnson, Joel E.; Torres, Marta E; Andreassen, Karin; Berndt, Christian; Bohrmann, Gerhard

doi:10.1038/s41467-017-02550-9

Cited by 126 publications

(143 citation statements)

References 71 publications

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“…On the other hand, a cubic unit of NGHs can contain approximately 180 cubic units of natural gas at standard temperature and pressure (Servio & Englezos, 2002). Therefore, NGHs have attracted much attention from academia, the industry, and the government, which has resulted in great research efforts on exploitation technology (depressurization, thermal stimulation, chemical inhibitor injection, CH 4 -CO 2 replacement, and fluidization mining method; Koh et al, 2016;Liu et al, 2017;Rutqvist et al, 2009;Tupsakhare et al, 2017;Wallmann et al, 2018;Wang et al, 2014), flow assurance (Gao, 2008;Gbaruko et al, 2007;Zerpa et al, 2011), and energy conversion (Yoneda et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Cementation Failure Behavior of Consolidated Gas Hydrate‐Bearing Sand

Liu

et al. 2020

JGR Solid Earth

111

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The macromechanical properties (strength, stiffness, stress-strain relationship, etc) of the hydrate-bearing sediment are often correlated with the hydrate cementation failure behavior. In this study, a consolidated drained triaxial shear test with X-ray computed tomography was conducted on a hydrate-bearing sediment with a hydrate saturation of 32.1% under 3 MPa effective confining pressure for revealing the cementation failure behavior. The hydrate occurrences were clearly identified to be cementing, grain-coating, prepatchy cluster and patchy cluster. The cementation failure behavior (morphology), deformation evolution (quantitative statistics), and localized shear deformation at different regions of stress-strain curve were observed and analyzed using computed tomography. In the linearity region, the hydrate-cemented clusters moved as a whole, while small hydrate particles would aggregate to the periphery of the clusters. The noncemented sand particles move disorderly during this process. Localized deformation occurred perfectly exhibit an antisymmetric bifurcation pattern. In the plasticity region, the specimen starts to deform plastically; an internal shear band occurs in the specimen. The hydrates begin to shed from the periphery of the cemented structure, and the grinding effect of hydrates begins to occur between sand particles. However, the shedded hydrates will not enter and fill the neighboring pores but hind the movement of sand particles structurally near the original position. In the yielding region, the hydrate-cemented cluster structure is completely damaged and crushed into small pieces; a shear band with a determined thickness and inclination angle was observed.

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Section: Introductionmentioning

confidence: 99%

Cementation Failure Behavior of Consolidated Gas Hydrate‐Bearing Sand

Liu

et al. 2020

JGR Solid Earth

111

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“…The observed variations in δ 13 C can be attributed to variable admixtures of methane‐derived and sedimentary carbon and different degrees of related consolidation and maturity. The carbonate δ 13 C generally fall into the range of porewater δ 13 C DIC (−10‰ to −40‰) found in the top 8 meters in this region, accompanied by δ 13 C CH 4 values ranging from −50 to −70‰ (VPDB) (Wallmann et al, 2018). Accordingly, carbonate crusts are highly likely a product of AOM coupled to the oxidation of biogenic methane (Greinert et al, 2001).…”

Section: Resultsmentioning

confidence: 98%

“…However, since the collected carbonates provided no clues on changes in the release rate of methane from the seafloor, additional methane release caused by global warming cannot be excluded. In 2016, a drilling expedition in the area revealed porewater freshening of sediments related to gas hydrate dissociation (Wallmann et al, 2018). Numerical modeling suggest that the destabilization of the hydrates started around 8,000 years before present, which coincided with the time when isostatic uplift due to postglacial rebound outpaced eustatic sea‐level rise, i.e., when hydrates became unstable due to depressurization.…”

Section: Introductionmentioning

confidence: 99%

Biogeochemical Consequences of Nonvertical Methane Transport in Sediment Offshore Northwestern Svalbard

et al. 2020

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A site at the gas hydrate stability limit was investigated offshore northwestern Svalbard to study methane transport in sediment. The site was characterized by chemosynthetic communities (sulfur bacteria mats, tubeworms) and gas venting. Sediments were sampled with in situ porewater collectors and by gravity coring followed by analyses of porewater constituents, sediment and carbonate geochemistry, and microbial activity, taxonomy, and lipid biomarkers. Sulfide and alkalinity concentrations showed concentration maxima in near‐surface sediments at the bacterial mat and deeper maxima at the gas vent site. Sediments at the periphery of the chemosynthetic field were characterized by two sulfate‐methane transition zones (SMTZs) at ~204 and 45 cm depth, where activity maxima of microbial anaerobic oxidation of methane (AOM) with sulfate were found. Amplicon sequencing and lipid biomarker indicate that AOM at the SMTZs was mediated by ANME‐1 archaea. A 1D numerical transport reaction model suggests that the deeper SMTZ‐1 formed on centennial scale by vertical advection of methane, while the shallower SMTZ‐2 could only be reproduced by nonvertical methane injections starting on decadal scale. Model results were supported by age distribution of authigenic carbonates, showing youngest carbonates within SMTZ‐2. We propose that nonvertical methane injection was induced by increasing blockage of vertical transport or formation of sediment fractures. Our study further suggests that the methanotrophic response to the nonvertical methane injection was commensurate with new methane supply. This finding provides new information about for the response time and efficiency of the benthic methane filter in environments with fluctuating methane transport.

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“…Bangs et al () combined analyses of bottom‐simulating reflectors in seismic data from Hydrate Ridge with a broad freshening signal in pore fluids at ODP Site 1247 to postulate an episode of gas hydrate destabilization that occurred ~4 to 8 ka, following postglacial warming. Similarly, a broad freshening signal in pore fluids recovered by MeBo drilling off Svalbard was attributed to an enhancement in gas hydrate dissociation driven by isostatic rebound (Wallmann et al, ).…”

Section: Factors Affecting Chloride Profilesmentioning

confidence: 98%

Sedimentation Controls on Methane‐Hydrate Dynamics Across Glacial/Interglacial Stages: An Example From International Ocean Discovery Program Site U1517, Hikurangi Margin

Screaton

Torres

Dugan

et al. 2019

Geochem Geophys Geosyst

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Dissolved chloride concentrations higher than seawater were observed over a broad depth range in pore water profiles from International Ocean Discovery Program Site U1517 on the Hikurangi Margin. This Cl maximum is not associated with an 87Sr/86Sr anomaly, indicating that it is not caused by hydration reactions during ash alteration. We use a numerical modeling approach to examine possible causes for recent gas hydrate formation that can result in the observed Cl high. Our approach considers sedimentation, sea level, and bottom water temperature (BWT) changes due to glaciation as drivers for the downward migration of the base of gas hydrate stability and gas hydrate formation. The modeling results reveal that lowering of sea level during glaciation can allow methane hydrate dissociation followed by postglacial hydrate formation as sea level rises. However, BWT cooling of 2 °C during glaciation followed by warming during deglaciation would mostly counteract the impacts of sea level change. Bottom water cooling during glaciation is expected in this region and many locations worldwide. As a result, our simulations do not support the previous hypotheses of large‐scale gas hydrate dissociation due to sea level drop during glaciation, which have been proposed as triggers for widespread gas release and slope failure. Such a mechanism is only possible where BWT remains constant or increases during glaciation. Our simulations indicate that sedimentation constitutes the largest factor driving recent methane hydrate formation at Site U1517, and we suggest that sedimentation may play a larger role in gas hydrate dynamics along margins than previously recognized.

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Gas hydrate dissociation off Svalbard induced by isostatic rebound rather than global warming

Cited by 126 publications

References 71 publications

Cementation Failure Behavior of Consolidated Gas Hydrate‐Bearing Sand

Cementation Failure Behavior of Consolidated Gas Hydrate‐Bearing Sand

Biogeochemical Consequences of Nonvertical Methane Transport in Sediment Offshore Northwestern Svalbard

Sedimentation Controls on Methane‐Hydrate Dynamics Across Glacial/Interglacial Stages: An Example From International Ocean Discovery Program Site U1517, Hikurangi Margin

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